Impact of light spectrum and photosynthetic photon flux density on the germination and seedling emergence of Okra

Abstract

Light's impact on many crop species and vegetables has been deeply studied in recent years but there are still some economic and technical issues to overcome. Thus, the impact of light spectrum and photosynthetic photon flux density from light-emitting diodes on the germination and seedling emergence of Okra has been investigated in this study. Different light treatments have been applied to Okra seeds using a factorial design of three levels of light spectrum and three levels of photosynthetic photon flux density; these three levels of light spectrum are defined by their peak wavelengths at 635 nm (R₆₃₅), 457 nm (B₄₅₇) and 521 nm (G₅₂₁) and are, respectively, in the red, blue and green region of the visible spectrum; levels of photosynthetic photon flux density are 100 µmol m⁻² s⁻¹, 200 µmol m⁻² s⁻¹ and 300 µmol m⁻² s⁻¹. Results show significant interactions between light spectrum and photosynthetic photon flux density on mean germination time, mean germination rate, uncertainty of germination and seedling emergence height. R₆₃₅ shows a better mean germination rate and less uncertainty and dispersion than B₄₅₇ and G₅₂₁. Seedlings that emerged under photosynthetic photon flux density of 300 µmol m⁻² s⁻¹ are significantly shorter than those that emerged under 100 µmol m⁻² s⁻¹ and 200 µmol m⁻² s⁻¹.